package thired.class08_tree;

import java.util.ArrayList;

public class Class09_MaxSubBSTSize {

    public static class Node {
        public int value;
        public Node left;
        public Node right;

        public Node(int data) {
            this.value = data;
        }
    }

    public static int getBSTSize(Node head) {
        if (head == null) {
            return 0;
        }
        ArrayList<Node> arr = new ArrayList<>();
        in(head, arr);
        for (int i = 1; i < arr.size(); i++) {
            if (arr.get(i).value <= arr.get(i - 1).value) {
                return 0;
            }
        }
        return arr.size();
    }

    public static void in(Node head, ArrayList<Node> arr) {
        if (head == null) {
            return;
        }
        in(head.left, arr);
        arr.add(head);
        in(head.right, arr);
    }

    public static int maxSubBSTSize1(Node head) {
        if (head == null) {
            return 0;
        }
        int h = getBSTSize(head);
        if (h != 0) {
            return h;
        }
        return Math.max(maxSubBSTSize1(head.left), maxSubBSTSize1(head.right));
    }

    public static int maxSubBSTSize2(Node head) {
        if (head == null) {
            return 0;
        }
        return process(head).maxSubBSTSize;
    }

    static class Info{
        public int maxSubBSTSize;
        public int size;
        public int max;
        public int min;

        public Info(int maxSubBSTSize, int size, int max, int min) {
            this.maxSubBSTSize = maxSubBSTSize;
            this.size = size;
            this.max = max;
            this.min = min;
        }
    }

    public static Info process(Node root){
        if(root == null){
            return  null;
        }

        Info left = process(root.left);
        Info right = process(root.right);

        int max = root.value;
        int min = root.value;
        if (left != null){
            max = Math.max(left.max,max);
            min = Math.min(left.min,min);
        }
        if(right != null){
            max = Math.max(right.max,max);
            min = Math.min(right.min,min);
        }
        int size = 1;
        if (left != null){
            size += left.size;
        }
        if(right != null){
            size += right.size;
        }
        int maxSubBSTSize = 0;
        if(left != null){
            maxSubBSTSize = Math.max(left.maxSubBSTSize,maxSubBSTSize);
        }
        if(right != null){
            maxSubBSTSize = Math.max(right.maxSubBSTSize,maxSubBSTSize);
        }
        if(
                (left == null || left.maxSubBSTSize == left.size)
        && (right == null || right.maxSubBSTSize == right.size)
        && (left == null ? true : left.max < root.value)
        && (right == null ? true : right.min > root.value)
        ){
            int p1 = left == null ? 0 : left.maxSubBSTSize;
            int p2 = right == null ? 0 : right.maxSubBSTSize;
            maxSubBSTSize = Math.max((p1 + p2 + 1),maxSubBSTSize);
        }

        return new Info(maxSubBSTSize,size,max,min);
    }



    // for test
    public static Node generateRandomBST(int maxLevel, int maxValue) {
        return generate(1, maxLevel, maxValue);
    }

    // for test
    public static Node generate(int level, int maxLevel, int maxValue) {
        if (level > maxLevel || Math.random() < 0.5) {
            return null;
        }
        Node head = new Node((int) (Math.random() * maxValue));
        head.left = generate(level + 1, maxLevel, maxValue);
        head.right = generate(level + 1, maxLevel, maxValue);
        return head;
    }

    public static void main(String[] args) {
        int maxLevel = 4;
        int maxValue = 100;
        int testTimes = 1000000;
        for (int i = 0; i < testTimes; i++) {
            Node head = generateRandomBST(maxLevel, maxValue);
            if (maxSubBSTSize1(head) != maxSubBSTSize2(head)) {
                System.out.println("Oops!");
            }
        }
        System.out.println("finish!");
    }


}
